As materials used for automotive lamp-peripheral parts, mainly thermosetting resins such as unsaturated polyester resins and bulk molding compounds (BMC), and aluminum-made materials are conventionally broadly used. Although thermosetting resins are better than aluminum-made materials in the point of being of a light weight, since the specific gravities exceed 2.0, further weight reduction is demanded. The thermosetting resins have peculiar problems such as the complexity of the post-handling work of molded articles and working environment pollution due to dusts. Therefore, as materials used for automotive lamp-peripheral parts, the conversion of materials is progressing from thermosetting resins and aluminum-made materials to thermoplastic resins, such as polyetherimide and high-heat resistant polycarbonate, on which aluminum vapor-deposition can be carried out directly. However, even these thermoplastic resins are insufficient in the aspect of light weight, and materials having lower specific gravities are desired in consideration of the environmental and energy-saving aspect.
Polyphenylene ether resins are excellent in mechanical properties, electric properties, acid resistance, alkali resistance and heat resistance, and simultaneously have various properties such as low specific gravities, low water absorption rates and good dimensional stability. Therefore, polyphenylene ether resins are broadly used as materials for household appliances, OA devices, business machines, information devices and automobiles; and particularly in the applications requiring high heat resistance and rigidity such as automotive lamp-peripheral parts, the demand for resin compositions designed in a higher ratio of the content of a polyphenylene ether resin is anticipated in future.
Particularly in the applications to automotive lamp extension members, there are not a few cases where good molding fluidity, a remarkably high light reflection property, and direct aluminum vapor-depositability are required. Therefore, properties of the polyphenylene ether resin composition are anticipated to include sufficient heat resistance, mechanical properties and good molding fluidity, and simultaneously include, particularly, the good surface appearance and brightness feeling of molded articles.
A method of improving the heat resistance and the mechanical properties of a thermoplastic resin containing a polyphenylene ether resin usually involves a method of adding inorganic fillers such as glass fibers, carbon fibers, mica and talc. However, since the method, even if the addition of the inorganic fillers is in a small amount, remarkably spoils the toughness which the resin intrinsically has, and the surface gloss of molded articles, a resin composition obtained by the method cannot be used in many applications, and is remarkably difficult to apply particularly to automotive extension members.
A method of imparting an impact resistance to a polyphenylene ether resin involves blending of a rubber-reinforced polystyrene (HIPS), which is widely carried out, but the brightness feeling of an obtained molded article is likely to be spoiled even with a small blend amount of the rubber-reinforced polystyrene, as in the case of the addition of inorganic fillers described above.
As a technology relevant to an automotive lamp extension members made by using a polyphenylene ether-based resin, there is already a disclosure of a resin composition, using a blended material of a polyphenylene ether and a liquid crystal polyester, excellent in the balance of light weight, heat resistance, fluidity and mechanical properties (for example, see Patent Document 1).
There is a disclosure of a technology of a resin composition containing a relatively high-concentration polyphenylene ether, the resin composition being improved in the heat aging resistance and the molded film appearance by adding a specific stabilizer and being suitable for applications to automotive lamp parts including an automotive lamp extension (for example, see Patent Document 2).